Lithium-ion batteries with nanostructured electrodes

ABSTRACT

Several embodiments related to lithium-ion batteries having electrodes with nanostructures, compositions of such nanostructures, and associated methods of making such electrodes are disclosed herein. In one embodiment, a method for producing an anode suitable for a lithium-ion battery comprising preparing a surface of a substrate material and forming a plurality of conductive nanostructures on the surface of the substrate material via electrodeposition without using a template. The substrate material is at least partially compliant.

BACKGROUND

Lithium-ion batteries are commonly used in consumer electronics becauseof their high energy-to-weight ratio, low or no memory effect, and longcharge-holding ability when not in use. In addition to applications inconsumer electronics, lithium-ion batteries are growing in popularityfor defense, automotive, and aerospace applications. These newapplications impose a continued need to improve the energy density oflithium-ion batteries.

Conventional lithium-ion batteries typically have a carbon-based anode.However, the carbon-based anode tends to limit the charging capacity ofthe lithium-ion batteries. For example, lithiation of a carbon-basedanode can produce a charging capacity of about 372 mA·h/g, whilelithiation of tin (Sn) can produce a charging capacity of about 990mA·h/g, and lithiation of silicon (Si) can produce a charging capacityof about 4,200 mA·h/g. However, lithiation (which may also be referredto as “insertion”) of lithium in both tin and silicon is known to beassociated with about 300% volume change. As a result, after a fewcharge-discharge cycles, a tin- or silicon-based anode would bepulverized, and thus the charging capacity of the lithium-ion batterywould be reduced. Accordingly, certain improvements in lithium-ionbattery design and construction are needed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a lithium-ion battery duringdischarging in accordance with embodiments of the technology.

FIG. 1B is a schematic diagram of a lithium-ion battery during chargingin accordance with embodiments of the technology.

FIG. 2 is a flowchart showing a method of manufacturing an anodesuitable for the lithium-ion battery of FIGS. 1A and 1B in accordancewith embodiments of the technology.

FIG. 3 is a scanning electron microscope (SEM) image of a sample formedaccording to several embodiments of the method of FIG. 2 in accordancewith embodiments of the technology.

FIG. 4 is another SEM image of a sample formed according to severalembodiments of the method of FIG. 2 in accordance with embodiments ofthe technology.

FIG. 5 is a composite transmission electron microscope (TEM) image of asample formed according to several embodiments of the method of FIG. 2in accordance with embodiments of the technology.

FIG. 6 is a perspective view of a lithium-ion battery formed duringtesting in accordance with embodiments of the technology.

FIG. 7 is a plot of discharging capacity versus number of dischargecycles for a sample formed according to several embodiments of themethod of FIG. 2 in accordance with embodiments of the technology.

FIG. 8 shows a series of high resolution photographs of reflectivity ofsamples with plating temperatures in accordance with embodiments of thetechnology.

FIG. 9 shows SEM images of samples plated at different temperatures inaccordance with embodiments of the technology.

FIG. 10 shows a SEM image and a schematic of a pyramid-shaped protrusionformed in a 70° C. sample in accordance with embodiments of thetechnology.

FIG. 11 is a SEM image of a sample formed according to severalembodiments of the method of FIG. 2 before undergoing charge/dischargecycles.

FIG. 12 is a SEM image of the sample in FIG. 11 after undergoing 100charge/discharge cycles.

FIG. 13A is a TEM image of a nanoneedle of the sample in FIG. 11.

FIG. 13B is a TEM image of the nanoneedle in FIG. 13A after 100charge/discharge cycles.

FIG. 14 schematically illustrate stages of a process for formingnanoneedles in the samples of FIG. 2.

FIG. 15A-E are SEM images of a sample undergoing the stages of FIG. 14.

FIGS. 16A and 16B show SEM images of a sample plated under a firstplating condition in accordance with embodiments of the technology.

FIGS. 17A and 17B show SEM images of a sample plated under a secondplating condition in accordance with embodiments of the technology.

FIG. 18 shows a SEM image of a sample plated under a third platingcondition in accordance with embodiments of the technology.

FIGS. 19A-19F show SEM images of samples having tin electroplated ontocompliant copper tapes under different magnification levels.

FIGS. 20A-20D show representative conductive polyester fibers under 100,300, 600, and 10,000 times magnifications, respectively.

FIGS. 21A-21E show a sample of tin electroplated onto conductivepolyester fiber material at different magnifications.

DETAILED DESCRIPTION

This document describes battery systems, devices, and associated methodsof making. In particular, several embodiments are related to lithium-ionbatteries having electrodes with nanostructures, compositions of suchnanostructures, and associated methods of making such electrodes.Several of the details set forth below are provided to describe thefollowing embodiments and methods in a manner sufficient to enable aperson skilled in the relevant art to practice, make, and use them.Several of the details and advantages described below, however, may notbe necessary to practice certain embodiments and methods of thetechnology. Additionally, the technology may include other embodimentsand methods that are within the scope of this disclosure but are notdescribed in detail.

This document describes battery systems, devices, and associated methodsof making. In particular, several embodiments are related to lithium-ionbatteries having electrodes with nanostructures, compositions of suchnanostructures, and associated methods of making such electrodes. Eventhough the technology is described below using a lithium-ion battery asan example, in other embodiments, the technology may be applicable inother types of batteries (e.g., containing sodium, potassium, calcium,magnesium, cadmium, or copper ions), a chemical sensor, an organic thinfilm transistor, an electromechanical actuator, a gas separationmembrane, a fuel cell, and/or other suitable electronic components.

Several of the details set forth below are provided to describe thefollowing embodiments and methods in a manner sufficient to enable aperson skilled in the relevant art to practice, make, and use them.Several of the details and advantages described below, however, may notbe necessary to practice certain embodiments and methods of thetechnology. Additionally, the technology may include other embodimentsand methods that are within the scope of this disclosure but are notdescribed in detail.

FIG. 1A is a schematic diagram of a lithium-ion battery 100 duringdischarging, and FIG. 1B is a schematic diagram of the lithium-ionbattery 100 during charging in accordance with embodiments of thetechnology. As shown in FIGS. 1A and 1B, the lithium-ion battery 100 caninclude a container 102 holding an anode 104, a cathode 106, anelectrolyte 108, and an optional membrane 110 in the electrolyte 108.Even though only certain components are illustrated in FIGS. 1A and 1B,in other embodiments, the lithium-ion battery 100 can also includeinsulators, gaskets, vent holes, and/or other suitable components (notshown). In further embodiments, the membrane 110 may be omitted.

In certain embodiments, the anode 104 can include an electricallyconductive substrate 105 and a plurality of one-dimensional tinnanostructures, e.g., tin nanoneedles covering 1% or more of thesubstrate 105 of the anode 104. As used hereinafter, the phrase“nanoneedles” generally refers to a one-dimensional nanostructure thathas a generally constant cross-sectional area or is tapered along atleast a portion of its length. Typical dimensions of nanoneedlesproduced according to the present technology are from about 2 μm toabout 5 μm in length, from about 20 μm to about 50 nm in width at thetip, and from about 50 nm to about 200 nm in width at the base. Thenanoneedle may also have other suitable dimensions other than theforegoing dimensions in other suitable applications. Examples of suchtin nanoneedles are shown in FIGS. 3 and 4.

In certain embodiments, the substrate 105 can include a generally rigidmaterial. For example, in one embodiment, the substrate 105 can includea copper plate, disc, or components of other suitable geometry. In otherembodiments, the substrate 105 can include a generally flexible or atleast partially compliant material. As used hereinafter, the phrases“flexible” or “at least partially compliant” generally refer to having acompliance of about 3.0×10⁻⁷ 1/Pa to about 8×10⁻¹² 1/Pa. For example, inone embodiment, the flexible substrate 105 can include a copper sheetwith a thickness less than about 0.07 mm. In other examples, thesubstrate 105 can include a metalized polymeric material. For instance,the substrate 105 can include at least one of polyester, nylon, carbonfiber, polyethylene, cellulose, lignin, Kevlar, urethane, elastomers,cotton, wool, silk, jute, soy, and/or other suitable polymeric or fabricmaterials. The polymeric or fabric materials can be coated, impregnated,embedded, threaded, and/or otherwise combined with an electricallyconductive material (e.g., a metal, a metal alloy, etc.) to be at leastpartially conductive. In further examples, the substrate 105 can includeother suitable types of flexible materials.

In certain embodiments, the tin nanoneedles can be produced byelectro-deposition in ambient air at temperatures less than about 50° C.without using any templates, as discussed in more detail below withreference to the Examples section. In other embodiments, the anode 104with the nanostructures can be formed via electroplating in anelectrolyte (e.g., about 0.2M to about 0.8M sodium stannate solution).Example electroplating conditions can include a pH of about 7.5 to about14, a current density of about 25 to about 45 mA/cm², a platingtemperature of about 35° C. to about 75° C., a soaking time of about 0min to about 60 min at a soaking temperature of about 25° C. to about75° C., and a plating time of about 5 min to about 15 min. In furtherembodiments, the anode 104 with the nanostructures may be formed withsimilar or different techniques with similar or different processingconditions.

In further embodiments, the anode 104 can also include a plurality ofnanowires, nanosprings, nanofibers, and/or other suitable one- ormulti-dimensional nanostructures constructed from zinc (Zn), palladium(Pd), tin-copper alloys, zinc-copper alloys, tin-gold alloys, tin-silveralloys, and/or other suitable materials. For example, in one embodiment,the nanostructures may be formed with generally pure elements that canbe electrodeposited and can alloy with lithium (Li) during batteryoperation. Examples of such elements include tin (Sn), zinc (Zn), lead(Pb), antimony (Sb), bismuth (Bi), silver (Ag), and gold (Au).

In another embodiment, the nanostructures may be formed with binary,ternary, or higher order mixtures of the elements that can beelectrodeposited and can alloy with lithium (Li) during batteryoperation. Examples of binary mixtures include Sn—Zn, Sn—Au, Sn—Sb,Sn—Pb, Zn—Ag, Sb—Ag, Au—Sb, Sb—Zn, Zn—Bi, Zn—Au. Examples of ternarymixtures include Sn—Zn—Sb, Sn—Zn—Bi, Sn—Zn—Ag, Sn—Sb—Bi, Sb—Zn—Ag,Sb—Zn—Au, Sb—Sn—Bi. An example of a quaternary mixture can includeSn—Zn—Sb—Bi.

In yet another embodiment, the nanostructures may be formed withintermetallic compounds of elements (e.g., the generally pure elementsdiscussed above) and other elements that can be electrodeposited and canalloy with lithium (Li) during battery operation. Examples of suchintermetallic compounds include Sn—Cu, Sn—Co, Sn—Fe, Sn—Ni, Sn—Mn,Sn—In, Sb—In, Sb—Co, Sb—Ni, Sb—Cu, Zn—Co, Zn—Cu, and Zn—Ni. In furtherembodiments, the nanostructures may be formed with mixtures of binarymixtures of elements that can be electrodeposited and can alloy withlithium (Li) during battery operation and any other element that can beco-electrodeposited. Examples of such electroplating scheme can includeSn—Zn—Co, Sn—Zn—In, Sn—Zn—Cu, Sn—Sb—Co, and Sn—Sb—In.

The cathode 106 can be constructed from a layered oxide (e.g., lithiumcobalt oxide (LiCoO₂)), a polyanion (e.g., lithium iron phosphate(LiFePO₄)), or a spinel (e.g., lithium manganese oxide (LiMn₂O₄)). Othersuitable materials for the cathode 106 can include lithium nickel oxide(LiNiO₂), lithium iron phosphate fluoride (Li₂FePO₄F), lithium cobaltnickel manganese oxide (LiCo_(1/3)Ni_(1/3)Mn_(1/3)O₂),Li(Li_(a)Ni_(x)Mn_(y)Co_(z))O₂, and/or other suitable cathode materials.

In certain embodiments, the electrolyte 108 can include a non-aqueoussolution of organic carbonates such as ethylene carbonate or diethylcarbonate containing complexes of lithium ions. The electrolyte 108 cancontain non-coordinating anion salts such as LiPF₆, LiAsF₆, LiCIO₄,LiBF₄, and lithium triflate. In other embodiments, the electrolyte 108may also include an aqueous and/or a partially aqueous solution oflithium salts and/or other suitable compositions.

As shown in FIG. 1A, during discharging, lithium ions 112 are extractedfrom the anode 104 and migrate toward the cathode 106 via theelectrolyte 108. The lithium ions 112 pass through the optional membrane110 and are inserted into the cathode 106. As a result, a current 114flows from the cathode 106 past a load 116 to the anode 104. As shown inFIG. 1B, during charging, a charger 118 provides a charging current 120to the cathode 106. The charging current 120 causes lithium ions 112 tobe extracted from the cathode 106 and move toward the anode 104. Thelithium ions 112 pass through the optional membrane 110 and are insertedinto the anode 104 via, e.g., alloying and/or otherwise combining withthe material of the anode 104.

Several embodiments of the lithium-ion battery 100 can have a highercharging capacity than conventional devices. For example, as discussedabove, a conventional lithium-ion battery with a carbon-based anode canhave a charging capacity of about 372 mA·h/g while several embodimentsof the lithium-ion battery 100 can have a charging capacity of about 990mA·h/g. As a result, the charging capacity of the lithium-ion battery100 may be improved when compared to conventional lithium-ion batteries.

Several embodiments of the anode 104 of the lithium-ion battery 100 canhave improved charging/discharging cyclability. Without being bound bytheory, it is believed that several embodiments of the anode 104 canaccommodate the large volume changes associated with lithium insertionbecause the one-dimensional nanostructures are generally freestanding.As a result, these freestanding structures or nanostructures may swellduring lithium insertion without causing pulverization and/or otherstructural damage to the anode 104 as a whole.

Indeed, it has been observed that a lithium-ion battery with severalembodiments of the anode 104 retained and even had improved chargingcapacity for a large number of charge/discharge cycles. For example, ata constant current of 50 μA, and a high charge/discharge rate of 400mA/g, about 300-400 mA·h/g of the charging capacity was maintainedduring 25 cycles. Even more surprising, the charging capacity actuallyincreased during the cyclic performance test, as discussed in moredetail below with reference to the Examples section.

FIG. 2 is a flowchart showing a method 200 of manufacturing an anodesuitable for the lithium-ion battery of FIGS. 1A and 1B in accordancewith embodiments of the technology. As shown in FIG. 2, an initial stage(block 202) of the method 200 can include preparing a substrate forelectrodeposition. In one embodiment, the substrate can include a copperfoil. In other embodiments, the substrate can include a wire, a coil, afoil, and/or other structures constructed from a metal (e.g., nickel(Ni)), a metal alloy (e.g., steel or brass), graphite, a polymer,ceramics, and/or other suitable materials.

In certain embodiments, preparing the substrate can include at least oneof (a) polishing the substrate (e.g., in a chemical-mechanical polishingprocess), (b) treating the substrate with a basic solution (e.g., sodiumhydroxide), and (c) treating the substrate with an acidic solution(e.g., sulfuric acid). In other embodiments, preparing the substrate canalso include treating the substrate with other suitable organic and/orinorganic solutions and/or other suitable processing operations.

Another stage (block 204) of the method 200 can then include formingconductive nanostructures on the substrate. In one embodiment, thenanostructures can be produced by electrodeposition in ambient air attemperatures less than about 50° C. without using any templates. Inother embodiments, nanostructures can be produced by electroplating inan electrolyte (e.g., a sodium stannate solution), as discussed abovewith reference to FIG. 1. In certain embodiments, the conductivenanostructures can be one-dimensional, e.g., nanoneedles. In otherembodiments, the nanostructures can also include a plurality ofnanowires, nanosprings, nanofibers, and/or other suitable one- ormulti-dimensional nanostructures.

In the illustrated embodiment, forming nanostructures on the substrateincludes two separate operations: growing a nucleation layer on thesubstrate (block 206) and forming nanostructures on the nucleation layervia electrodeposition (block 208). In other embodiments, formingnanostructures may include both of these operations in a singleelectrodeposition stage. In further embodiments, forming nanostructurescan also include growing the nanostructures via chemical vapordeposition, atomic vapor deposition, physical vapor deposition, and/orother suitable techniques.

Another stage (block 210) of the method 200 can also include adjustingat least one deposition condition such that nanostructures with targetstructural characteristics are formed on the substrate. In oneembodiment, adjusting at least one deposition condition includesadjusting at least one of (a) a deposition temperature, (b) a depositioncurrent density, (c) a deposition environment (e.g., chemicalcomposition of deposition electrolyte), and (d) agitation (or the lackthereof) during deposition. For example, in one embodiment, growing anucleation layer on the substrate can be at a first temperature (e.g.,50° C.), and forming nanostructures on the nucleation layer can be at asecond temperature (e.g., 45° C.). In other embodiments, the firstand/or second temperatures can also be at 55° C., 60° C., 65° C., 70°C., 75° C., 80° C., 85° C., and/or other suitable temperatures. Infurther embodiments, other suitable deposition conditions may also beadjusted.

The method 200 can then include a decision at block 212 of whether theprocess may continue. If further deposition is desired, then the processreverts to forming conductive nanostructures on the substrate in block204; otherwise, the process ends.

Several embodiments of the method 200 are simple, readily implemented,and inexpensive to operate because they utilize electrodepositiontechniques without templates. Conventional bottom-up synthesis ofnanostructures typically includes atom-by-atom deposition that requiresprecise control. For example, vapor transport and deposition have beenused to synthesize one-dimensional nanowires, nanobelts, andnanoribbons. These processes are expensive to operate and have lowyield, at least in part because these processes require vacuumprocessing at high temperatures.

Another conventional technique for synthesizing one-dimensionalnanostructures by electrodeposition uses a template on a substratesurface to obtain a desired morphology. For example, thetemplate-assisted synthesis of metal nanowires and nanotubes includesdeposition of metal into cylindrical pores or channels of an inert andnonconductive nanoporous substrate. The template greatly affects thesize and shape of the deposited nanostructures. However, one drawback ofthe template-assisted synthesis is the difficulty in preparing suitabletemplates. Furthermore, such techniques require multiple operations andare frequently not scalable.

Several tests were conducted to form a lithium-ion battery generallysimilar to the lithium-ion battery 100 of FIGS. 1A and 1B following amethod generally similar to the method 200 of FIG. 2. The formedlithium-ion battery was tested for cyclability and charging capacity.The results of the test show that the formed lithium-ion battery hassignificantly improved cyclability when compared to conventionaldevices.

EXAMPLE 1

Substrate material: pure Cu foils (99.99% pure, Alfa Aesar Inc.), size:25 mm×25 mm×1 mm. Coupons were cut from the Cu foils and polished usingstandard metallographic techniques. Prior to electroplating, thesubstrates were cleaned in a sodium hydroxide solution at 50° C. andthen immersed in concentrated sulfuric acid to remove surface oxide. Thesubstrates were then electroplated under the following conditions:

-   Electrolyte: Sodium tin (IV) oxide—142 g per liter solution    -   Sodium hydroxide—15 g per liter solution        Plating conditions were monitored, and typical values are listed        below:    -   1. Temperature: 35° C. to 85° C.    -   2. Current density: 45 mA/cm² to 70 mA/cm²    -   3. Film thickness: 1 μm to 10 μm    -   4. Solution agitation    -   5. Distance between electrodes: 1 inch    -   6. Surface finish of substrate: as received, polished with 0.05        μm alumina suspension, and scratched.

FIGS. 3 and 4 are SEM photos of a sample formed in the foregoing platingprocess. As shown in FIGS. 3 and 4, the plated tin formed a plurality ofrandomly extending nanoneedles. FIG. 5 shows a TEM image of a singlenanoneedle that was removed from the substrate. The current density usedto obtain the nanostructures depicted in FIGS. 3, 4, and 5 was 46mA/cm². The electroplating process was started at 50° C., and thetemperature was then decreased to 45° C. after 2 minutes. The totalplating time was 7 minutes and 54 seconds. The substrate surface waspolished with an 0.05 μm alumina suspension. The distance between theelectrodes was 1 inch, and the electrolyte was stirred during theelectroplating process.

FIG. 6 is a perspective view of a lithium-ion battery formed duringtesting in accordance with embodiments of the technology. Thelithium-ion battery was formed as a coin cell assembled in anargon-filled glove box using a sample formed as discussed above as anelectrode, Celgard 480 as a separator, 1M LiPF₆ in ethylene carbonate(EC)/dimethyl carbonate (DMC) (1:1 volume ratio, Aldrich) aselectrolyte, and lithium foil (Alfa Aesar Inc.) as a counter electrode.Testing was done galvanostatically at a current of 50 μA. At a constantcurrent of 50 μA, and a high charge/discharge rate of 400 mA/g, about300-400 mA·h/g of the discharging capacity was maintained during 25cycles. As shown in FIG. 7, the discharging capacity actually increasedduring a portion of the cyclic performance test.

EXAMPLE 2

In another test, the effect of the temperature of the electrodepositionprocess on the size, shape, and morphology of surface features wasstudied. The surface morphology (as described by plating thickness,grain shape, size, and orientation) depends on various plating variablesuch as film thickness, current density, type of anion, platingtemperature, solution agitation, and/or other variables.

Plates of Cu, 25 mm×25 mm×1 mm, were cut and polished using standardmetallographic techniques. Prior to electroplating, the substrates werecleaned in a sodium hydroxide solution maintained at 50° C. and thenimmersed in concentrated sulfuric acid to remove any surface oxide. Theprepared plates were electroplated with tin using an alkalineelectrolyte of the following composition: 142 g sodium tin (IV) oxideper liter of solution and 15 g sodium hydroxide per liter of solution.Plating was conducted for about 240 seconds (for a thickness of 5 mm) ata current density of 50 mA/cm². The temperature of the plating wasvaried between 35° C. to 85° C.

The samples were washed and dried immediately after electroplating andexamined visually as well as by using a FEI Sirion field emissionscanning electron microscope (FESEM) equipped with an energy dispersivespectrometry (EDS) system and operated at 10 kV to 20 kV. The sampleswere subsequently aged at room temperature in air. All aged samples wereperiodically examined using the FESEM.

FIG. 8 is a series of high-resolution photographs showing the variationin brightness (reflectivity) of the samples with different platingtemperatures. The sample plated at 25° C. appears dull (lowreflectivity), whereas the sample plated at 85° C. appears brightest.The brightness of the plated samples increased with the increase inplating temperature.

FIG. 9 shows SEM images of samples plated at different temperatures. Asshown in FIG. 9 a, the surface of the sample plated at 35° C. is veryirregular and highly porous. This is consistent with the poorreflectivity of the sample in FIG. 8. At plating temperatures of 45° C.,55° C., and 70° C. (FIG. 9 b-e), pyramid-shaped features formed on thesurface. These pyramid-shaped features were identified to be pure tin.The underlying film became increasingly smooth with increases intemperature.

Without being bound by theory, during electrodeposition, every time ametal ion is discharged from the electrolyte, a high temperature adatomis generated. These adatoms contact the substrate surface and finally“freeze” to form a solid film. It is believed that the cooling rate atleast influences or determines the extent of grain growth and theresulting grain size of the plated structures. The higher thetemperature of the plating solution (substrate), the slower the coolingrate of these adatoms. Thus, at higher temperatures, the adatoms candiffuse for longer distances on the substrate surface before freezing.Therefore, with an increase in the plating temperature, the grain sizeincreases and the film surface becomes increasingly smooth. Increasingthe plating temperature to 85° C. resulted in the formation of largefaceted grains (FIG. 9 f).

It is also believed that surface protrusions form during electroplatingafter a certain critical thickness when there is an accumulation ofmetal ions. In the initial stages of plating, the metal ions areuniformly distributed over the substrate. After a certain thickness, ametal-ion denuded layer (MIDL) is created over the surface. Thethickness of the MIDL varies due to the variation in the dischargeactivity along the substrate surface. Metal ions are suppliedpreferentially through thinner MIDL regions, ultimately resulting in thenucleation of surface protrusions.

As noted above, the underlying surface became increasingly smooth withincreases in temperature. This would decrease the number of sites wherethe adatoms can be adsorbed. Hence, the number of nucleation sites andnucleation rates of the pyramidal features would decrease with anincrease in plating temperature. It is believed that the smaller thenumber of nucleation sites, the faster protrusions can grow. After theprotrusions nucleate, new metal ions get preferentially discharged attheir tip due to high local current density. The size of thepyramid-shaped surface features indeed increased with increases inplating temperature, whereas their density decreased as shown in FIGS. 9b-9 d.

It is also believed that the pyramid-shaped protrusions formed in orderto minimize the overall surface energy by exposing the lowest energyplane of tin. The crystal structure of tin is tetragonal, and it belongsto the space group I41/amd. The lowest surface energy planes of such astructure are believed to be the {101} planes. Therefore, these pyramidswill be bound by four equivalent {101} surfaces. FIG. 10 shows ahigh-resolution SEM image and a schematic of one of the pyramid-shapedprotrusions formed in a 70° C. sample. Faceted grain boundaries (shownby white arrows in FIG. 10 a) similar to those seen in 85° C. samplesare seen in the underlying film.

Experiments were conducted to test the cycle response of the formedsamples. FIG. 11 is a SEM image of a sample formed according to severalembodiments of the method of FIG. 2 before undergoing charge/dischargecycles, and FIG. 12 is a SEM image of the sample after undergoing 100charge/discharge cycles. FIG. 13A is a TEM image of a nanoneedle of thesample in FIG. 11 before charge/discharge, and FIG. 13B is a TEM imageof the nanoneedle in FIG. 13B after 100 charge/discharge cycles. Asshown in FIGS. 11-13B, the formed nanoneedles generally maintained theirstructural integrity and shape after 100 charge/discharge cycles.

FIG. 14 illustrates stages of a process for forming nanoneedles in thesamples of FIG. 2. In the illustrated example, a copper substrate wasused with copper oxide (Cu₂O) surface layers for forming tin (Sn)nanoneedles. In other examples, other suitable substrate materialsand/or nanoneedles may also be formed following similar process stages.

As shown in FIG. 14, at stage I, copper oxide is formed on the surfaceof the copper substrate via oxidation. At stage II, a thin tin seedlayer is formed on the copper oxide surface layer. Subsequently, atstage III, tin nanoneedles grow from the tin seed layer to formdifferent “branches.”

FIG. 15A-E are SEM images of a sample undergoing the stages of FIG. 14.As shown in FIG. 15A, copper oxide crystals formed on the coppersubstrate when the substrate was ‘soaked’ in an electrolyte for 60minutes. As shown in FIG. 15B, electroplating tin on the coppersubstrate for 67 seconds (1 μm intended thickness) resulted in generallycomplete coverage of the copper oxide crystals and the formation of atin seed layer. As shown in FIG. 15C, further increasing the platingtime resulted in instability in the tin seed layer. As a result, sometin nanoneedles grew in the regions of high instability. FIG. 15C showsformation of some tin nanoneedles when the plating time was 5 minutes 37seconds. As shown in FIG. 15D, the surface density of tin nanoneedlesincreased with further increase in the plating time. FIG. 15D showsnanoneedles that formed upon ‘soaking’ and plating for 11 minutes 15seconds.

EXAMPLE 3

In another set of tests, the effect of electrolyte concentration andsoaking time on formation of nanostructures were studied. The followingconditions are common to the tests:

-   -   Electrolyte: alkaline sodium stannate solution    -   pH: 13.5    -   Plating time: 11 min 15 sec    -   Plating temperature: 50° C.    -   Soak temperature: 50° C.        During a first test, 0.45M alkaline sodium stannate solution        with zero soaking time was used. As shown in FIGS. 16A and 16B,        the formed nanostructures had short and thick nanoneedles with        low area coverage density. During a second test, 0.668M alkaline        sodium stannate solution with zero soaking time was used. As        shown in FIGS. 17A and 17B, the formed nanostructures had long        and thin nanoneedles distributed in larger clusters with a        higher area coverage density than that in FIGS. 16A and 16B.        During a third test, 0.668M alkaline sodium stannate solution        with 30 min soaking was used. As shown in FIG. 18, the formed        nanostructures had long and thin needles with a higher area        coverage density than those formed without soaking in FIGS.        16A-17B. Accordingly, based on the results of these tests, at        least one of the foregoing conditions for electroplating may be        adjusted or controlled based on a target structure and/or an        area coverage density of the nanostructures.

EXAMPLE 4

Several tests were conducted to form nanoneedles on an at leastpartially compliant substrate material following a method generallysimilar to the method 200 of FIG. 2. The tests show that nanoneedles(e.g., tin nanoneedles formed during the tests) may be suitably formedon metalized at least partially compliant substrate materials (e.g.,copper tapes, polyester fabrics, etc.). For example, FIGS. 19A-19F showSEM images of samples having tin electroplated onto copper tapespurchased from 3M of St. Paul, Minn., under different magnificationlevels. FIGS. 20A-20D show sample polyester fibers without electroplatedtin under 100, 300, 600, and 10,000 times magnifications, respectively.FIGS. 21A-21E show samples with tin electroplated on a similar polyestermaterial under different magnifications.

From the foregoing, it will be appreciated that specific embodiments ofthe technology have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. In addition, many of the elements of one embodiment may becombined with other embodiments in addition to or in lieu of theelements of the other embodiments. Accordingly, the disclosure is notlimited except as by the appended claims.

1. A method for producing an anode suitable for a lithium-ion battery,the method comprising: preparing a surface of a substrate, the substratebeing at least partially compliant and having a compliance of about3.0×10⁻⁷ to 8×10⁻¹² 1/Pa; forming a plurality of conductivenanostructures on the surface of the substrate via electro-deposition;and controlling at least one operating condition of theelectrodeposition based on a target profile for the plurality ofconductive nanostructures formed on the surface of the substrate, thetarget profile including the conductive nanostructures forming aplurality freestanding structures.
 2. The method of claim 1 whereinforming a plurality of conductive nanostructures includes forming aplurality of conductive nanostructures on the surface of the substratevia electrodeposition without using a template at a temperature greaterthan about 40° C.
 3. The method of claim 1 wherein forming a pluralityof conductive nanostructures includes forming a plurality of conductivenanoneedles on the surface of the substrate via electrodepositionwithout using a template.
 4. The method of claim 1 wherein forming aplurality of conductive nanostructures includes forming a plurality oftin (Sn) nanoneedles on the surface of the substrate viaelectrodeposition without using a template.
 5. The method of claim 1wherein forming a plurality of conductive nanostructures includesforming a plurality of tin (Sn) nanoneedles on the surface of thesubstrate via electrodeposition without using a template, and whereinthe substrate includes copper with surface copper oxide (Cu₂O), and hasa thickness less than 0.07 mm.
 6. A lithium-ion battery, comprising: acathode; an electrolyte in electrical communication with the cathode,the electrolyte containing lithium ions; and an anode spaced apart fromthe cathode and in electrical communication with the electrolyte,wherein the anode includes an at least partially compliant substrate anda material alloyable with lithium carried by the at least partiallycompliant substrate, the material alloyable with lithium forming aplurality of one dimensional or multi-dimensional nanostructures spacedapart from one another on at least a portion of a surface of the atleast partially compliant substrate of the anode, the at least partiallycompliant substrate having a compliance of about 3.0×10⁻⁷ to 8×10⁻¹²1/Pa.
 7. The lithium-ion battery of claim 6 wherein the nanostructuresinclude at least one of generally pure tin (Sn), zinc (Zn), lead (Pb),antimony (Sb), bismuth (Bi), silver (Ag), or gold (Au).
 8. Thelithium-ion battery of claim 6 wherein the nanostructures include atleast one of a binary mixture of Sn—Zn, Sn—Au, Sn—Sb, Sn—Pb, Zn—Ag,Sb—Ag, Au—Sb, Sb—Zn, Zn—Bi, or Zn—Au.
 9. The lithium-ion battery ofclaim 6 wherein the nanostructures include at least one of a ternarymixture of Sn—Zn—Sb, Sn—Zn—Bi, Sn—Zn—Ag, Sn—Sb—Bi, Sb—Zn—Ag, Sb—Zn—Au,or Sb—Sn—Bi.
 10. The lithium-ion battery of claim 6 wherein thenanostructures include a quaternary mixture of Sn—Zn—Sb—Bi.
 11. Thelithium-ion battery of claim 6 wherein the nanostructures includeintermetallic compounds of at least one of Sn—Cu, Sn—Co, Sn—Fe, Sn—Ni,Sn—Mn, Sn-ln, Sb-ln, Sb—Co, Sb—Ni, Sb—Cu, Zn—Co, Zn—Cu, or Zn—Ni. 12.The lithium-ion battery of claim 6 wherein the nanostructures include atleast one of Sn—Zn—Co, Sn—Zn-ln, Sn—Zn—Cu, Sn—Sb—Co, or Sn—Sb-ln.
 13. Abattery, comprising: a first electrode; an electrolyte in electricalcommunication with the first electrode, the electrolyte containing aplurality of metal ions; and a second electrode spaced apart from thefirst electrode and in electrical communication with the electrolyte,wherein the second electrode contains an at least partially compliantsubstrate and a material combinable with the metal ions on at least aportion of a surface of the second electrode, the material forming aplurality of freestanding nanostructures spaced apart from one another,wherein the substrate has a compliance of about 3.0×10⁻⁷ to 8×10⁻¹²1/Pa.
 14. The battery of claim 13 wherein the plurality of freestandingnanostructures include a plurality of freestanding nanoneedles.
 15. Thebattery of claim 13 wherein the plurality of freestanding nanostructuresinclude a plurality of freestanding nanoneedles individually having agenerally constant cross-sectional area.
 16. The battery of claim 13wherein the plurality of freestanding nanostructures include a pluralityof freestanding nanoneedles extending along an axis, at least a portionof one of the freestanding nanoneedles being tapered along the axis. 17.The battery of claim 13 wherein the plurality of freestandingnanostructures include a plurality of freestanding nanoneedles extendingalong an axis, a first portion of one of the freestanding nanoneedleshaving a generally constant cross-sectional area, and a second portionof one of the freestanding nanoneedles having tapered along the axis.18. The battery of claim 13 wherein the second electrode furtherincludes a substrate on at least a portion of the surface of the secondelectrode, and wherein at least a portion of the plurality offreestanding nanostructures extends away from the substrate.
 19. Thebattery of claim 13 wherein the second electrode further includes asubstrate on at least a portion of the surface of the second electrode,a first one of the freestanding nanostructures extending away from thesubstrate and a second one of the freestanding nanostructure extendingaway from the first one of the freestanding nanostructures.
 20. Themethod of claim 1, wherein the substrate includes a polymeric or fabricmaterial including an electrical conductive material.
 21. The battery ofclaim 6, wherein the at least partially compliant substrate includes apolymeric or fabric material including an electrical conductivematerial.
 22. The battery of claim 13, wherein the at least partiallycompliant substrate includes a polymeric or fabric material including anelectrical conductive material to be at least partially conductive. 23.The battery of claim 6, wherein the at least partially compliantsubstrate includes copper with surface copper oxide (Cu₂O), and thesubstrate has a thickness less than 0.07 mm.
 24. The battery of claim13, wherein the at least partially compliant substrate includes copper,and the substrate has a thickness less than 0.07 mm.
 25. A method forproducing an anode suitable for a lithium-ion battery, the methodcomprising: preparing a surface of a substrate, the substrate being atleast partially compliant, the substrate including a polymeric or fabricmaterial including an electrical conductive material; forming aplurality of conductive nanostructures on the surface of the at leastpartially compliant substrate via electro-deposition; and controlling atleast one operating condition of the electrodeposition based on a targetprofile for the plurality of conductive nanostructures formed on thesurface of the substrate, the target profile including the conductivenanostructures forming a plurality freestanding structures.
 26. Alithium-ion battery, comprising: a cathode; an electrolyte in electricalcommunication with the cathode, the electrolyte containing lithium ions;and an anode spaced apart from the cathode and in electricalcommunication with the electrolyte, wherein the anode includes an atleast partially compliant substrate and a material alloyable withlithium carried by the substrate, the material alloyable with lithiumforming a plurality of nanostructures spaced apart from one another onat least a portion of a surface of the at least partially compliantsubstrate of the anode, the at least partially compliant substrateincluding a polymeric or fabric material including an electricalconductive material.
 27. The lithium-ion battery of claim 26, whereinthe at least partially compliant substrate includes a metalized polymer.